Clean catalyticoxidation of 8-hydroxyquinoline to quinoline-5,8-dione with tBuOOH in the presence of covalently bound FePcS–SiO2catalysts

Abstract

The clean catalytic oxidation of 8-hydroxyquinoline (8-HQ) with tert-butyl hydroperoxide to quinoline-5,8-dione (QD), a molecular framework fragment of antitumor compounds, over silica-supported iron tetrasulfophthalocyanine catalysts (FePcS) is reported. The pronounced influence of the FePcS state (monomer vs. dimer) and the support (amorphous SiO₂vs. mesoporous MCM-41) on the catalytic activity and selectivity is revealed. Depending on the catalyst structure, turnover frequency values determined from the initial rates of 8-HQ consumption varied from 215 to 3570 h⁻¹.The effects of solvent, temperature, reagent concentrations and catalyst amounts on the substrate conversion and QD selectivity were studied to optimize the reaction conditions. With an optimal catalyst, the yield of the target product reached 66%. The truly heterogeneous nature of the catalysis was also demonstrated.